1. Field of the Invention
The present invention relates to a sheet-supply device and an image forming apparatus incorporating the sheet-supply device.
2. Discussion of the Background
Certain sheet-supply devices installed in image forming apparatuses such as copiers, printers, facsimile machines and multifunction peripherals machines (MPF) use a roll of paper, that is, a single rolled long sheet.
In one example of a sheet-supply device proposed in JP-2001-302051-A, when a new roll of paper is installed in the sheet-supply device so that a recording sheet from the roll of paper can be supplied, a distal end of the sheet from the roll of paper is manually sent to a supply roller along a guide member provided in a main body of the sheet-supply device.
FIG. 20 is a schematic diagram illustrating a known sheet-supply device 800 using a roll of paper 500. In FIG. 20, reference numeral 100 designates a sheet that is pulled out from the roll of paper 500, 200 designates an upper guide, 300 designates a lower guide, and 400 designates a pair of supply rollers. The upper guide 200 and the lower guide 300 function as guide members.
In this example, in order to install a new roll of paper 500 into the sheet-supply device 800 so that the sheet 100 unreeled from the roll of paper 500 can be supplied, the sheet 100 pulled out from the roll of paper 500 is inserted between a tip 200a of the upper guide 200 and a tip 300a of the lower guide 300, and a distal end of the sheet 100 is passed between the upper guide 200 and the lower guide 300 to the pair of supply rollers 400. An entrance sensor (not shown) is provided in front of the pair of the supply rollers 400 (left side in FIG. 21A). When the entrance sensor detects the sheet 100, the pair of supply roller 400 rotates, the distal end of the sheet 100 is clamped between the pair of supply rollers 400, and thus, the sheet 100 can be supplied.
However, in the sheet-supply device 800 shown in FIG. 20, as the sheet 100 is supplied and the sheet remaining in the roll 500 is reduced, as shown in FIG. 21A, the position of the sheet 100 unreeled from an outer circumferential face of the roll 500 is moved from a position A shown in FIG. 21A to a position A′ shown in FIG. 21A. Accordingly, a supply route of the sheet 100 is changed from a route indicated by the broken line shown in FIG. 21A to a route indicated by the solid line shown in FIG. 21A. As a result, the sheet 100 strongly interferes with the tip 200a of the upper guide 200, and the sheet 100 is damaged, which is a problem. Furthermore, as shown in FIG. 21B, when the supply of the sheet 100 is continued and the sheet 100 is fully unreeled from the roll 500, an adhesion portion between a proximal end of the sheet 100 and a core of the roll 500 is exposed. At this time, the sheet 100 further strongly interferes with the tip 200a of the upper guide 200, which causes load for the sheet 100 to be greatest.
In order to prevent these problems, as shown in FIG. 22 a short length of an upper guide 201 can be used in a sheet-supply device 801 to alleviate interference between the sheet 100 pulled from the roll 500 and the upper guide 201.
However, in the configuration in which the upper guide 201 is shortened, when the sheet 100 unreeled from a new roll 500 is set in the sheet-supply device 801, the degree of visibility of a tip 201a of the upper guide 201 is low from outside because the tip 201a is hidden by the new roll 500 indicated by broken lines shown in FIG. 22. Accordingly, the distal end of the sheet 100 unreeled from the new roll 500 is less likely to be inserted into a gap between the upper guide 201 and the lower guide 300, and it becomes difficult to visually detect whether or not the sheet 100 of the roll 500 is correctly set in the sheet-supply device 801.
In view of foregoing, interference between a sheet and a guide member is undesirable, and accordingly, there is a need for a technology to realize improving workability and visibility when the sheet is set in a sheet-supply device in an image forming apparatus.